Core B: Biochemistry The Biochemistry Core provides specimen processing and chemical determinations on serum, urine, stool, and dietary specimens. It also is responsible for acquiring stool, urine, and blood specimens for mailing to outside reference laboratories. Assays routinely carried out include calcium, phosphorus, protein, creatinine, hydroxyproline, FSH, 25- hydroxyvitamin D, 1,25 dihydroxyvitamin D, bone Gla protein, estradiol, as well as radiochemical determinations of 45Ca and 47Ca. As a general biochemistry laboratory, this core laboratory is equipped to provide a number of other chemical determinations, such as fecal fat, serum strontium, and certain other tests, including urine sodium and potassium.